Following [1], I will briefly sketch the derivation of the flow equation for the scale-dependent effective action, which generates the 1PI correlation functions. The chiral Ising and chiral Heisenberg universality class, relevant for phase transitions to CDW and SDW in two-dimensional Dirac materials, will serve as an example for the calculation of critical behavior in terms of the fRG[2]. Furthermore to establish a connection, the fRG approach will be compared to a more standard Wilsonian scheme close to the upper critical dimension of the system.
[1] arXiv:hep-ph/0611146
[2] Phys. Rev. B 89, 205403 (2014), arXiv:1402.6277